Kept making fucked up noises time to time, and could only get a solid 3 hours gameplay before it started saying GAME COULD NOT BE READ (only a few scratches on San Andreas). And it's the old big fat ps2's. Worked fine for all those years.
Depends on mod, like that graphics one for GTA IV was pretty amazazazing.
But yeh I've never really bothered with mods except in Diablo 2 really.
That said SA: MP is awesome in that it lets you play with others and really opens up a lot of options for customisation (as said endless possibilities) and is more like a feature that would have been nice to come with (or be officially patched into) the game.